This can be caused by a number of things but the one that fixed our issue was to just uninstall and reinstall Revit. There are still other factors so I have outlined them below.

Check the desktop shortcut and make sure the target has ENU after Language. Right click on the desktop icon and go to Properties. Example from my desktop shortcut: "C:\Program Files\Autodesk\Revit 2019\Revit.exe" /language ENU

Navigate to the C:\Users\your user profile folder\AppData\Roaming\Autodesk\Revit\Autodesk Revit 2019 or whichever version you are using and open the Revit.ini in Notepad. Search for the line Language and make sure below it shows ENU: * AppData is a hidden folder. Here is Microsoft's steps on how to show hidden folders https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

[Language]

Select=ENU

Reset the Revit user interface by deleting the UIState.dat found in C:\Users\your user profile folder\AppData\Roaming\Autodesk\Revit\Autodesk Revit 2019\ENU. Make sure you create a backup by copying the UIState.dat before deleting.

If you are still not able to access your cloud projects through Revit do the following to troubleshoot:

Verify you are assigned to a seat of BIM 360 Design from with the manage.autodesk.com. If you are not the Contract Manager (Primary Admin) or Software Coordinator (Secondary Admin) in your office for the Autodesk software you will need to ask them to verify this for you.

Verify you have been added to the BIM 360 Docs folder permissions. There are thee areas where a user will need to be added.

First in the Account Admin Members list.

Second invited to the project on the Project Admin module.

Third given permission to the folder with the Document Management module.

Sign out of Revit and close it. If the Autodesk Desktop app is running sign out of that and exit out of it.

Delete as much as you can from the temp folder located here: C:\Users\your user profile folder\AppData\Local\Temp. If something will not let you delete it click Skip.AppData is a hidden folder. Here is Microsoft's steps on how to show hidden folders

Launch Revit and have another user sign into your Revit who has access to the cloud models. If the user is also not able to access the cloud models on your machine add the Revit Cloud trusted sites and reboot your machine.

launch Revit and sign in as yourself to test. You can also test with another user signing into your Revit.